On May 11, 2010, at 8:28 PM, CARSON DEAN FENIMORE wrote:

Just FYI: The problem appears to have gone away with some minor
changes.  We have twisted in use in a large application, which
consists of many threads.  These threads were invoking some
twisted-related methods; for example, calling addCallback on a
Deferred instance from one thread, while running a deferredGenerator
in twisted -- this, of course, is not thread safe!  Except for a
handful of such cases, we were using twisted correctly - adding
callbacks on the main thread solved the issue at hand.

Glad you solved your problem, and thanks for reporting your conclusions here so future readers don't have to wonder what the heck was going on! :)